Fuel cells, for example, hydrogen fuel cells, are one possible alternative energy source for powering vehicles. In general, fuel cells include a negative electrode (anode), an electrolyte, and a positive electrode (cathode). In a proton exchange membrane fuel cell (PEMFC), the electrolyte is a solid, proton-conducting membrane that is electrically insulating but allows protons to pass through. Typically, the fuel source, such as hydrogen, is introduced at the anode using a bipolar or flow field plate where it reacts with a catalyst and splits into electrons and protons. The protons travel through the electrolyte to the cathode and the electrons pass through an external circuit and then to the cathode. At the cathode, oxygen in air introduced from another bipolar plate reacts with the electrons and the protons at another catalyst to form water. One or both of the catalysts are generally formed of a noble metal or a noble metal alloy, typically platinum or a platinum alloy.
The bipolar plates in the PEMFC have two primary functions. First, the bipolar plates feed reactant gases (e.g., hydrogen and air) to the membrane electrode assembly (MEA). Second, the bipolar plates collect current from the MEA. In order to collect current, the bipolar plates must be conductive or have a conductive coating. Typically, the bipolar plates are formed from a conductive carbon-based material, such as a carbon composite, which may be fabricated by a molding process.